a) Field of the Invention
The present invention relates to a device for confirming the adjustment of an automotive headlamp optical axis, and more particularly, to a device for confirming the optical-axis adjustment of an automotive headlamp, adapted to confirm mainly the horizontal adjustment of optical axis by checking the movement of a rod fixed to a reflector of the headlamp in relation to a case fixed to a lamp housing of the headlamp, and provided with a means of protecting the case and rod against any external shock, for example, such as a pebble flying from outside during driving of the car or tool dropped by mistake during a car servicing.
b) Prior-art Statement
If directed too far upward, a headlamp will provide a light beam which is likely to dazzle the driver of a car running in the opposite lane, possibly causing a danger. On the contrary, if the headlamp is directed too far downward, the headlamp will not provide sufficient illumination of the road surface in front of the car for assurance of safe driving visibility. Also, if directed excessively to the right or left of the car, the headlamp will not illuminate the road surface sufficiently. Hence, the automotive headlamp has to be equipped with devices for fine vertical and horizontal adjustment, respectively, of the optical axis of the headlamp actually installed on a car.
A typical one of the automotive headlamps of this type is known from the disclosure in U.S. Pat. No. 5,055,980, in which a reflector is pivotably mounted inside a lamp housing of the headlamp by means of a pivot bearing, a lamp bulb assembly is fixed to the reflector and vertical and horizontal optical-axis adjusters for the headlamp are fixed to the reflector and lamp housing. These vertical and horizontal optical-axis adjusters are used to pivot the reflector vertically and horizontally in relation to the lamp housing, thereby adjusting the headlamp optical axis vertically and horizontally.
The direction of the headlamp optical axis must be adjusted with a high accuracy but cannot easily be adjusted except by a specialist using a special facility. Before a car is shipped from the automobile manufacturing facility or when the headlamps are equipped on a car at a service shop, the direction of the headlamp optical axis is adjusted by a specialist using a dedicated adjusting facility. However, the optical axis of the can headlamp, found deviated from its due direction for any reason after adjusted at such works or shop, must be readjusted.
In this case, some reference is available for such readjustment. Namely, if the optical axis of the headlamp has already been adjusted accurately, it can be readjusted without any specialist and special facility by reproducing its initially adjusted state. For this purpose, there have so far been proposed and used various types of optical-axis adjustment confirming devices (more specifically, devices for confirming whether or not the initially adjusted state of the optical axis has been reproduced).
A typical one of the devices for confirming mainly the horizontal adjustment of headlamp optical axis is known from the disclosure in the Japanese Unexamined Utility Model Publication No. Hei 4-24210, in which a hollow cylindrical case, open at one end thereof and closed at the other end and made of a transparent material through which the interior can be viewed, is fixed at the one-end (open) portion thereof at the edge of a through-hole in the lamp housing of an automotive headlamp in such a manner that it can initially be set, the other-end (closed) portion of the case being projected of the lamp housing; a rod is provided which is fixed at one end thereof to the reflector of the headlamp and inserted at the other-end portion thereof into the case from the open end of thereof; and the rod has marked on the other-end portion thereof a scale which faces an index on the case so that a displacement of the rod caused by a pivoting of the reflector can be read as a measure for adjustment of the optical axis.
The optical-axis adjuster is used to pivot the reflector with respect to the lamp housing, thereby adjusting the optical axis of the headlamp vertically or horizontally. As the reflector is pivoted, the rod is moved correspondingly. The moving distance of the rod is read as an adjustment of the headlamp optical axis by checking the displacement of the scale on the rod in relation to the index on the case. For this reading, it is assumed for example that the pivot angle of the reflector is 0.38.degree. when the displacement of the index by one graduation of the scale on the rod is 1.5 mm.
In such a device for confirmation of the optical axis adjustment, the rod is inserted axially movably in the case. So the rod is thin and mechanically weak. Since the case is fixed to the lamp housing so as to be initially settable, it has no sufficient rigidity against an external shock.
In the aforementioned optical-axis adjustment confirming device, however, the case, the rod, etc., are exposed outside the lamp housing and any protective means is not provided against external shock. The optical-axis adjustment confirming device will possibly be broken if given an external shock such as a tool dropped by mistake or a pebble flying from the road.